Pivoting high flux x-ray target and assembly

ABSTRACT

A high flux X-ray tube anode target assembly ( 101 ). The assembly includes a support shaft ( 107 ) connected to a pivot assembly ( 109 ). The assembly further includes a movable anode target ( 105 ) having a target surface ( 106 ) disposed at one end of the support shaft. The target surface includes a single radius of curvature. The radius of curvature extends from a pivot point ( 110 ). The assembly also includes a drive member ( 119 ) operably arranged with respect to the support shaft to provide motion to the anode target. The assembly is configured to maintain a substantially fixed distance between the pivot point and the target surface.

FIELD OF THE INVENTION

This disclosure relates to an X-ray tube anode target assembly and, moreparticularly, to configuration and structures for imparting pivotingmotion to an X-ray tube anode target assembly.

BACKGROUND

Ordinarily an X-ray beam-generating device referred to as an X-ray tubecomprises dual electrodes of an electrical circuit in an evacuatedchamber or tube. One of the electrodes is an electron emitter cathodewhich is positioned in the tube in spaced relationship to an anodetarget. Energization of the electrical circuit generates a stream orbeam of electrons directed towards the anode target. This accelerationis generated from a high voltage differential between the anode andcathode that may range from 60-450 kV, which is a function of theimaging application. The electron stream is appropriately focused as athin beam of very high velocity electrons striking the anode targetsurface. The anode surface ordinarily comprises a predeterminedmaterial, for example, a refractory metal so that the kinetic energy ofthe striking electrons against the target material is converted toelectromagnetic waves of very high frequency, i.e. X-rays, which proceedfrom the target to be collimated and focused for penetration into anobject usually for internal examination purposes, for example,industrial inspection procedures, healthcare imaging and treatment, orsecurity imaging applications, food processing industries. Imagingapplications include, but are not limited to, Radiography, CT, X-rayDiffraction with Cone and Fan beam x-ray fields.

Well-known primary refractory and non-refractory metals for the anodetarget surface area exposed to the impinging electron beam includecopper (Cu), Fe, Ag, Cr, Co, tungsten (W), molybdenum (Mo), and theiralloys for X-ray generation. In addition, the high velocity beam ofelectrons impinging the target surface generates extremely high andlocalized temperatures in the target structure accompanied by highinternal stresses leading to deterioration and breakdown of the targetstructure. As a consequence, it has become a practice to utilize arotating anode target generally comprising a shaft supported disk-likestructure, one side or face of which is exposed to the electron beamfrom the thermionic emitter cathode. By means of target rotation, theimpinged region of the target is continuously changing to avoidlocalized heat concentration and stresses and to better distribute theheating effects throughout the structure. Heating remains a majorproblem in X-ray anode target structures. In a high speed rotatingtarget, heating must be kept within certain proscribed limits to controlpotentially destructive thermal stresses particularly in compositetarget structures, as well as to protect low friction, solid lubricated,high precision bearings that support the target.

Only about 1.0% of the energy of the impinging electron beam isconverted to X-rays with the remainder appearing as heat, which must berapidly dissipated from the target essentially by means of heatradiation. Accordingly, significant technological efforts are expendedtowards improving heat dissipation from X-ray anode target surfaces. Formost rotating anode targets heat management must take place principallythrough radiation and a material with a high heat storage capacity.Stationary anode target body configurations or some complex rotatinganode target configurations may be designed to have heat transferprimarily take place using conduction or convection from the target tothe x-ray tube. Life of rotating x-ray targets are often gated by thecomplexities of rotation in a vacuum. Traditional x-ray target bearingsare solid lubricated, which have relatively low life. Stationary targetsdo not have this life-limiting component, at the cost of lowerperformance.

Other rotation components, solid lubricated bearings, ferro-fluid seals,spiral-grooved liquid metal bearings, etc, all introduce manufacturingcomplexity and system cost.

What is needed is a high flux X-ray tube configuration that providesoscillating motion to the target and includes components capable ofmaintaining an extended life, with a limited introduction of cost andmanufacturing complexity.

SUMMARY OF THE DISCLOSURE

One aspect of the present disclosure includes a high flux X-ray tubeanode target assembly. The assembly includes a support shaft connectedto a pivot assembly. The assembly further includes a movable anodetarget having a target surface disposed at one end of the support shaft.The target surface includes a single radius of curvature. The radius ofcurvature extends from a pivot point. The assembly also includes a drivemember operably arranged with respect to the support shaft to providemotion to the anode target. The assembly is configured to maintain asubstantially fixed distance between the pivot point and the targetsurface.

Another aspect of the disclosure includes an X-ray tube assembly havingan envelope having at least a portion thereof substantially transparentto X-ray. A cathode assembly is operatively positioned in the envelopewith an anode assembly. The anode assembly includes a support shaftconnected to a pivot assembly and a movable anode target having a targetsurface disposed at one end of the support shaft, the target surfacehaving a single radius of curvature. The radius of curvature extendsfrom a pivot point. A drive member is operably arranged with respect tothe support shaft to provide motion to the anode target and the assemblyis configured to maintain a substantially fixed distance between thepivot point and the target surface.

Another aspect of the disclosure includes a method for providing heatmanagement to an X-ray assembly. The method includes providing an X-raytube assembly having an envelope having at least a portion thereofsubstantially transparent to X-ray. The assembly also includes a cathodeassembly, operatively positioned in the envelope. The assembly alsoincludes an anode assembly having a support shaft connected to a pivotassembly and a movable anode target having a target surface disposed atone end of the support shaft, the target surface having a single radiusof curvature. The radius of curvature extends from a pivot point. Adrive member is operably arranged with respect to the support shaft toprovide motion to the anode target. The method further includes pivotingthe anode target assembly and maintaining a substantially fixed distancebetween the pivot point and the target surface.

The position of the focal point along the surface of the target isvaried, providing improved heat management, wherein the heat may bedissipated more easily. In addition, the increased dissipation permitsthe use of higher power and longer durations than are available with theuse of a stationary anode arrangement. In addition, the anode hasincreased life over anodes that have a fixed focal point on the anode.The anode target motion provides longer life than solid lubricatedbearings used in known rotating anode sources.

Another advantage of the present disclosure includes the reduction orelimination in dwell or delay time for anode motion reducing oreliminating heat build up due to reversal of direction. In addition,cooling may be accomplished primarily or exclusively through radiativecooling.

Still another advantage of the present disclosure is that the motion maybe provided by simple control algorithms and low torque requirements forthe drive assembly. In addition, compensation for slight alignment andoperating errors can easily be incorporated into the control and/ordesign.

Additionally, the assembly will have reduced manufacturing complexity,and cost, in comparison to conventional rotational bearing arrangements.

The assembly of the present disclosure may allow multiple spots to beplaced on a single target, in that each region will be thermallyisolated from the neighboring spot, while maintaining the benefit ofhigher power through oscillatory motion from a single drive mechanism.

Embodiments of the present disclosure also allow the distribution ofheat over a larger area of the anode target, through the oscillatingmotion, which reduces the peak temperature and maintains the temperaturebelow the evaporation limit for the metal in the envelope, and reducesthe temperature gradient between surface and substrate.

Other features and advantages of the present disclosure will be apparentfrom the following more detailed description of the preferredembodiment, taken in conjunction with the accompanying drawings whichillustrate, by way of example, the principles of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an elevational side view of an X-ray tube assemblyaccording to an embodiment of the present disclosure.

FIG. 2 shows a top perspective view of an X-ray tube assembly accordingto an embodiment of the present disclosure.

FIG. 3 shows an elevational view of a pivot assembly according to anembodiment of the present disclosure.

FIG. 4 shows an oscillatory coupling according to an embodiment of thepresent disclosure.

FIG. 5 shows a view of an anode assembly taken along line 5-5 of FIG. 4according to an embodiment of the present disclosure.

FIG. 6 shows an anode target assembly according to an embodiment of thepresent disclosure.

FIG. 7 shows a view of an anode target assembly taken along line 7-7 ofFIG. 6 according to an embodiment of the present disclosure.

FIG. 8 shows an anode target assembly according to another embodiment ofthe present disclosure.

FIG. 9 shows a view of an anode target assembly taken along line 9-9 ofFIG. 8 according to an embodiment of the present disclosure.

Wherever possible, the same reference numbers will be used throughoutthe drawings to refer to the same or like parts.

DETAILED DESCRIPTION

FIG. 1 is a schematic elevational view of an X-ray tube assembly 100having an anode assembly 101 and a cathode assembly 103. The anodeassembly 101 and cathode assembly 103 are arranged in a manner, throughthermionic or field-emission electron generation, that permits formationof X-rays, during X-ray tube assembly 100 operation. The anode assembly101 includes an anode target 105 mounted on a support shaft 107. Theanode target 105 is fabricated from any material suitable for use as ananode target, such as, but not limited to copper (Cu), iron (Fe), silver(Ag), chromium (Cr), cobalt (Co), tungsten (W), molybdenum (Mo), andtheir alloys. For example, tungsten or molybdenum having additiverefractory metal components, such as, tantalum, hafnium, zirconium andcarbon may be utilized. The suitable materials may also include oxidedispersion strengthened molybdenum and molybdenum alloys, which mayfurther include the addition of graphite to provide additional heatstorage. Further still, suitable material may include tungsten alloyshaving added rhenium to improve ductility of tungsten, which may beadded in small quantities (e.g., 1 to 10 wt %).

The support shaft 107 is mounted on a pivot assembly 109 with one ormore oscillatory couplings 111 (see e.g., FIGS. 4-5). The oscillatorycoupling 111 includes a first segment 401 (see FIG. 4) that is attachedto the support shaft 107 and a second segment 403 (see FIG. 4) of theoscillatory coupling 111 attached to the pivot assembly 109, ispermitted to oscillate. The use of a plurality of oscillatory couplings111 permits the anode target 105 to pivot about a center pivot point 110with rotation about two axes. The pivot point 110 is a point about whichaxis of pivoting or rotation intersect or otherwise the point aboutwhich the pivoting or rotation takes place. By “pivot”, “pivoting” andgrammatical variations thereof, it is meant to be a rotary or turningmotion about a single location or single area. By “oscillatory”,“oscillation” and grammatical variations thereof, it is meant to includeswaying motion to and fro, rotation or pivoting on an axis between twoor more positions and/or motion including periodic changes in direction.

The anode target 105 includes a target surface 106, which is curved witha single radius of curvature across the entire target surface 106.Although FIG. 1-2 includes a spherical segment geometry for the targetsurface 106, other geometries may be utilized as long as the radius ofcurvature remains fixed across the entire target surface. Other suitablegeometries include, but are not limited to spherical, hemi-spherical,semi-spherical, partial spherical, or spherical segment geometry. Thetarget surface 106 is the surface onto which an electron beam 112 isdirected. The electron beam 112 is directed to the target surface 106from cathode assembly 103.

The cathode assembly 103 comprises an electron emissive portion 113. Thedisclosure is not limited to the arrangement shown, but may be anyarrangement and/or geometry that permits the formation of an electronbeam at the electron emissive portion 113. Conductors or other currentsupplying mechanism may be included in the cathode assembly 103 tosupply heating current to a filament and/or conductor present in thecathode assembly for maintaining the cathode at ground or negativepotential relative to the anode target 105 of the tube assembly 100. Anelectron beam 112 from the electron emissive portion 113 impinges upontarget 105 at a focal point on the target surface 106 to produceX-radiation. The target surface 106 is configured with a substantiallyuniform radius of curvature to provide a substantially constant angle ofimpingement by the electron beam 112, throughout the anode target 105motion. The beam 112 produces X-radiation by impingement on target 105,wherein the X-radiation is directed through window 121.

At least a portion of the envelope 123 acts as a window 121 for theX-rays. The window 121 may be fabricated from glass or other materialsubstantially transparent to X-rays. The configuration of the envelope123 may be any configuration suitable for providing the X-radiation tothe desired locations and may be fabricated from conventionally utilizedmaterials.

The focal point may be a single point or an area having any suitablegeometry corresponding to the electron emissions from the electronemissive potion 113. Additionally, the focal point may have movementintroduced into the beam from electrostatic, magnetic or other steeringmethod. In addition, the focal point may be of constant size and/orgeometry or may be varied in size and/or geometry, as desired for theparticular application. “X-ray”, “X-radiation” and other grammaticalvariations as utilized herein mean electromagnetic radiation with awavelength in the range of about 10 to 0.01 nanometers or other similarelectromagnetic radiation. Heat is generated along the target surface106 at the point of electron beam contact (i.e., the focal point). Theanode target 105 is oscillated by drive assembly 115, which may include,but is not limited to, an induction or otherwise magnetically ormechanically driven drive mechanism. Suitable drive assemblies 115 mayinclude, but are not limited to, voice-coil actuators or switchedreluctance motors (SRM) drive. The drive assembly 115 may furtherinclude cams or other structures to convert linear, rotational or othermotion to oscillatory motion.

The drive assembly 115 includes an arrangement capable of providingoscillatory motion to the target 105. In the arrangement shown, thedrive assembly 115 includes a magnetically driven motor arrangement,including fixed stator portions 117 and a movable ball portion 119. Themovable ball portion 119 is preferably a ferromagnetic or otherwisemagnetic material that is capable of attraction to the stator portions117 upon electromagnetic activation thereof. The ball portion 119 isdisposed at a distal end of the support shaft 107 to the target 105. Thedrive assembly 115 is operably arranged to provide the oscillatorymotion for the attached target 105. The present disclosure is notlimited to the arrangement of drive assembly 115 shown and may includeany arrangement capable of providing pivoting motion to the target 105.

The movement of the target 105 provided by the drive assembly 115 issuch that the focal point on the target surface 106 provides asubstantially constant X-ray emission, wherein the target 105 movesrelative to the focal point. In addition, the angle of incidence for theelectron beam is maintained during anode target motion 105.Specifically, the drive assembly 115 provides motion to target 105 suchthat the focal point remains at a substantially fixed distance from theelectron emissive portion 113 and/or the angle at which the electronbeam impinges the target 105 remains substantially constant. The presentdisclosure is not limited to reflection based geometry for X-raygeneration, but may include alternate configurations, such as anodetarget 105 configured for transmission generated X-rays. The anodeassembly 101 and the cathode assembly 103 are housed in an envelope 123,which is under vacuum or other suitable atmosphere.

FIG. 2 shows a top perspective view of an X-ray tube assembly 100 havingsubstantially the same arrangement as shown and describe in FIG. 1. Asshown in FIG. 2, the pivot assembly 109 permits pivoting of the supportshaft 107, which thereby moves anode target 105. Further, the driveassembly 115 includes a plurality of stator portions 117 arranged in asubstantially circumferential arrangement about the ball portion 119.The activation of the stator portions 117 induces the anode target 105pivoting motion. The use of a plurality of oscillatory couplings 111permits the anode target 105 to pivot about a center pivot point 110with rotation about two axes. One skilled in the art would alsounderstand that this pivotal motion may also be provided utilizingbearing configurations. The drive assembly 115 may be controlled by anysuitable control arrangement including microprocessor or other controldevice, wherein the motions may be controlled to provide the desiredpivoting motion in order to provide a focal path 700 (see e.g., FIGS. 7and 9) that permits heat dissipation and minimize or eliminate heatgenerated damage to the target surface 106.

FIG. 3 shows a pivot assembly 109 according to an embodiment of thepresent disclosure. The pivot assembly 109 is configured to allow thepivoting of the support shaft 107 supported in opening 301. Fouroscillatory couplings 111 are arranged to provide pivoting of thesupport shaft 107 about two axes. The arrangement of the oscillatorycouplings 111 includes two oscillatory couplings 111 affixed to a firstpivot support member 303 and a second pivot support member 305. Thearrangement of the oscillatory couplings 111 between the first pivotsupport member 303 and a second pivot support member 305 permitsoscillatory motion about a first axis 304. In addition, the arrangementof the oscillatory couplings 111 includes two oscillatory couplings 111affixed to the second pivot support member 305 and a third pivot supportmember 307, onto which the support shaft 107 is mounted. The first axis304 and second axis are arranged substantially perpendicular to eachother. The arrangement of the oscillatory couplings 111 between thesecond pivot support member 305 and a third pivot support member 307permits oscillatory motion about a second axis 306. The first rotationalmotion 309 is about first axis 304 and the second rotational motion 311is about second axis 306. The combination of the rotations permitspivoting of the anode target 105 through large range of motion. WhileFIG. 1-3 shows four oscillatory couplings 111, the present invention mayutilize any number of oscillatory couplings 111 that provide the desiredpivoting movement of the anode target 105.

FIG. 4 shows an oscillatory coupling 111 for use in an embodiment of thedisclosure. The oscillatory coupling 111 provides a spring-like back andforth oscillatory motion 402 between segments 401, 403 of theoscillatory coupling 111. The oscillatory coupling 111 includes a firstsegment 401 that rotates with respect to a second segment 403 by segmentoscillation 402. During oscillation, the second segment 403 remainssubstantially stationary. In particular, the second segment 403 isattached to a fixture or other support that retards movement of thesecond segment 403, while first segment 401 is permitted to oscillate.FIG. 5 shows oscillatory coupling 111 taken along 5-5 of FIG. 4. Theoscillatory coupling 111 provides oscillatory motion 402 by a couplingmechanism 501 between the first segment 401 and the second segment 403.The coupling mechanism 501 may be one or more spring or force providingor otherwise flexible devices that provide connection between segments401, 403 and reciprocating motion between segments 401, 403. In theembodiment shown in FIGS. 1-3, a linear spring is utilized to provideflexing sufficient to provide oscillatory motion 402. The oscillatorycoupling mechanism 501 may include linear springs selected to introducemotion that may be varied for desired frequency, angle and path radii.

Coupling mechanisms 501, for example, utilizing linear springs toprovide oscillation, may have up to infinite life spans for a prescribedradial load and oscillating angle, which life spans are difficult orimpossible in known rotary motion assemblies. During operation of X-raytube assembly 100, the drive assembly 115, which is configured to pivotthe target 105 in a manner that results in flexing of the couplingmechanism 501 of the corresponding oscillatory couplings 111, which,permits motion of the first segment 401 (i.e. oscillation 402) withrespect to the second segment 403. The oscillation of the first segment401 provides target 105 with motion desirable for heat management.

FIG. 6 shows an anode target assembly 101 according to anotherembodiment of the present disclosure. The anode target assembly 101shown has a similar arrangement to the arrangement shown in FIG. 1,including a drive assembly 115 (not shown) to provide a rotationalmotion 311 about first axis 304. The target surface 106 includes aspherical segment, wherein the spherical segment includes a portion of asphere. The target assembly 101 includes two oscillatory couplings 111mounted to the housing or other structure within the X-ray tube assembly100 (see e.g., FIG. 1). The oscillatory couplings 111 mounted to thehousing are further mounted to another oscillatory coupling 111 mountedon support shaft 107. The use of a plurality of oscillatory couplings111 permits the anode target 105 to pivot about a center pivot point 110with rotation about two axes. The oscillatory couplings 111 are arrangedto permit oscillatory motion about first axis 304 and about second axis306. In addition, the embodiment shown in FIG. 6 includes a driveassembly 115′, which, like drive assembly 115, includes a stator portion117 and a ball portion 119. The ball portion 119 is connected to driveassembly 115′ and provides a rotational motion 309 about second axis306. The resulting pivoting motion permits movement of the anode target105 through a range of motion. The pivoting motion is constrained suchthat the target surface 106 remains at a fixed, single radius ofcurvature 601. The motion of the anode target 105 provides a movingfocal point or focal path 700 (see e.g., FIG. 7), which permitsdissipation of heat over a large area of target surface 106.

FIG. 7 shows a view of an anode target assembly taken along line 7-7 ofFIG. 6 according to an embodiment of the present disclosure. The targetsurface 106 preferably provides an aspect angle to which the electronbeam 112 impinges (see e.g., FIGS. 1-2) that is substantially constantand directs the X-radiation in the desired direction throughout themotion of the target 105. Since the position along the anode target 105(i.e., focal path 700) is varied, the heat generated by the impingementof the electrons on the anode target 105 is permitted to dissipate overa larger area. This dissipation of heat permits the use of higher powerand longer durations than are available with the use of a stationaryanode arrangement. The target 105 is not limited to the geometry shownand may include segmented or otherwise curved geometry anode targets105, for example, while not so limited, targets 105 may have a“butterfly” shape, or a multi-spot curved geometry, provided the targetsurface utilized maintains the substantially constant radius ofcurvature 601.

FIG. 8 shows an anode target assembly 101 according to anotherembodiment of the present disclosure. The anode target assembly 101shown has a similar arrangement to the arrangement shown in FIG. 1,including a drive assembly 115 (not shown) to provide a rotationalmotion 309 about first axis 304 and second axis 306. The use of aplurality of oscillatory couplings 111 permits the anode target 105 topivot about a center pivot point 110 with rotation about two axes. Thepivoting motion is provided by a pivot assembly 109 made up of a ring801 having an arrangement of four oscillatory couplings 111. Two of theoscillatory couplings 111 are mounted to the housing or other structurewithin the X-ray tube assembly 100 (see e.g., FIG. 1). Another twooscillatory couplings 111 are arranged with portions affixed to the ring801 and support shaft 107, respectively. The resulting pivoting motionpermits movement of the anode target through a range of motion. Thepivoting motion is constrained such that the anode surface 106 remainsat a fixed, single radius of curvature 601. The motion of the anodetarget 105 provides a moving focal point or focal path 700 (see e.g.,FIG. 9), which permits dissipation of heat over a large area of targetsurface 106.

FIG. 9 shows a view of an anode target assembly 101 taken along line 7-7of FIG. 6 according to an embodiment of the present disclosure. Thetarget surface 106 includes a spherical segment, wherein the sphericalsegment includes a portion of a sphere bounded by two substantiallyparallel planes passing through the sphere. The target surface 106preferably provides an aspect angle to which the electron beam 112impinges (see e.g., FIGS. 1-2) that is substantially constant anddirects the X-radiation in the desired direction throughout the motionof the target 105. Since the position along the anode target surface 106(i.e., focal path 700) is varied, the heat generated by the impingementof the electrons on the anode target 105 is permitted to dissipate overa larger area. This dissipation of heat permits the use of higher powerand longer durations than are available with the use of a stationaryanode arrangement.

Also, as discussed above, the particular arrangement of oscillatorycouplings 111 or other pivoting structures is not limited thearrangements shown and may include any pivoting or oscillatory motionproviding structure that is capable of pivoting the anode target in atleast two axes. Further, the present disclosure is not limited topivoting motion provided through the use of a plurality of oscillatorycoupling 111, but also includes direct actuation of the anode target 105in a motion maintaining a fixed distance from the pivot point. Forexample, the anode target 105 may be affixed to a drive assembly 115,wherein the drive assembly 115 provides reciprocating rotation oroscillation of the anode target 105, such that the target surface 106provides substantially constant production of X-rays from the electronbeam 112. Further a cam or similar device may be utilized to translateadditional rotational or other motion to the anode target 105. Inaddition, the present disclosure is not limited to the geometry of thetargets shown and may include target geometries that are asymmetrical orother non-circular arrangements. Further still, the present disclosureis not limited to a single focal point and may include multiple focalpoints.

While the disclosure has been described with reference to a preferredembodiment, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the disclosure. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the disclosure without departing fromthe essential scope thereof. Therefore, it is intended that thedisclosure not be limited to the particular embodiment disclosed as thebest mode contemplated for carrying out this disclosure, but that thedisclosure will include all embodiments falling within the scope of theappended claims.

1. An X-ray tube anode target assembly comprising: a support shaftconnected to a pivot assembly; a movable anode target having a targetsurface disposed at one end of the support shaft, the target surfacehaving a single radius of curvature, the radius of curvature extendingfrom a pivot point; a drive member operably arranged with respect to thesupport shaft to provide motion to the anode target; and wherein theassembly is configured to maintain a substantially fixed distancebetween the pivot point and the target surface.
 2. The anode assembly ofclaim 1, wherein the target surface is configured with a sphericalsegment geometry.
 3. The anode assembly of claim 1, wherein the targetsurface is configured to provide a reflection X-ray generation.
 4. Theanode assembly of claim 1, wherein the target surface is configured toprovide a transmission X-ray generation.
 5. The anode assembly of claim1, wherein the target is arranged at an angle to the cathode assembly,the angle remaining substantially constant during oscillatory motion. 6.Anode assembly of claim 1, wherein the target has two or more segmentseach comprising the target surface.
 7. The anode assembly of claim 1,wherein the drive member includes an induction motor to provideoscillation to the target.
 8. An X-ray tube assembly comprising: anenvelope having at least a portion thereof substantially transparent toX-ray; a cathode assembly, operatively positioned in the envelope withan anode assembly comprising: a support shaft connected to a pivotassembly; a movable anode target having a target surface disposed at oneend of the support shaft, the target surface having a single radius ofcurvature, the radius of curvature extending from a pivot point; a drivemember operably arranged with respect to the support shaft to providemotion to the anode target; and wherein the assembly is configured tomaintain a substantially fixed distance between the pivot point and thetarget surface.
 9. The X-ray tube assembly of claim 8, wherein thetarget surface is configured with a spherical segment geometry.
 10. TheX-ray tube assembly of claim 8, wherein the cathode assembly and targetsurface are configured to provide a single focal point.
 11. The X-raytube assembly of claim 8, wherein the cathode assembly and targetsurface are configured to provide multiple focal points.
 12. The X-raytube assembly of claim 8, wherein the target surface is configured toprovide a reflection X-ray generation.
 13. The X-ray tube assembly ofclaim 8, wherein the target surface is configured to provide atransmission X-ray generation.
 14. The X-ray tube assembly of claim 8,further comprising an oscillatory coupling between the drive member andthe target.
 15. The X-ray tube assembly of claim 14, wherein theoscillatory coupling includes a substantially linear coupling.
 16. TheX-ray tube assembly of claim 8, wherein the target is arranged at anangle to the cathode assembly, the angle remaining substantiallyconstant during motion.
 17. The X-ray tube assembly of claim 8, whereinthe drive member includes an induction motor to provide oscillation tothe target.
 18. A method for providing heat management to an X-rayassembly comprising: providing an X-ray tube assembly having: anenvelope having at least a portion thereof substantially transparent toX-ray; a cathode assembly, operatively positioned in the envelope; ananode assembly comprising: a support shaft connected to a pivotassembly; a movable anode target having a target surface disposed at oneend of the support shaft, the target surface having a single radius ofcurvature, the radius of curvature extending from a pivot point; a drivemember operably arranged with respect to the support shaft to providemotion to the anode target; and pivoting the anode target assembly andmaintaining a substantially fixed distance between the pivot point andthe target surface.
 19. The method of claim 18, wherein the pivotingincludes a rotationally motion about an axis substantially parallel tothe support shaft.
 20. The method of claim 18, wherein the pivotingincludes an oscillatory motion about two substantially perpendicularaxes.